Cylinder valve outlet connections types

Cylinders require the installation of a valve that will permit the withdrawal of the mixture. The valve used on a cylinder for a given mixture must be selected so the materials of construction are compatible with ail mixture components. The type of valve, packed or diaphragm, is chosen based on the integrity and regulatory requirements of the mixture. The outlet connection is selected based on the physical and chemical characteristics of the components. CGA V-7, Standard Method of Determining Cylinder Valve Outlet Connections for Industrial Gas Mixtures, is a guide for the selection of outlet connections for mixtures. It includes numerous examples of how to apply the selection procedures [12]. 

The cylinder valve outlet connection may be one of many types. In the United States and Canada the Compressed Gas Association (CGA) has established standard outlet valve connections for most gases, hereafter referred to as CGA connection. 

In the United States and several other countries, the industry has developed standardized cylinder valve outlet and inlet connections, transfer connections, and regulator connections for specific types and groups of compressed gases to prevent the misapplication of these potentially hazardous materials. 

Pressurized gas ancillary equipment downstream from the cylinder valve outlet is joined to the system piping by various types of threaded connections. Such equipment includes pressure reducing regulators, gauges, flowmeters, and station valves (for example, manifold isolation valves, etc.). 

When a cylinder contains a mixture of gases, valve selection criteria are more complex. Each component of the mixhore has its own hazardous properties, and two different components can present two different types of hazard. The standard procedure for choosing valve outlet connections in such cases is covered in CGA V-7, which considers the fire hazard, toxicity, state, and corrosiveness of each component. Most of the mixtures of interest to readers of this volume are subject to CGA V-7 an exception is nuxtures of medical gases, which are covered instead by CGA V-1. 

For further information on cylinder valve inlet connections and other thread types presently in use, that is. Special Gas Taper Threads (SGT) and National Gas Straight Threads (NGS), refer to CGA V-1, American National, Canadian, and Compressed Gas Association Standard for Compressed Gas Cylinder Valve Outlet and Inlet Connections, [1]... 

The single piston reciprocating pump was the first of its type to be used in liquid chromatographs, it is the simplest, the least expensive, and is still very popular today. The single piston pump is shown at the top of Figure 2. The piston is made of synthetic sapphire in fact, most pistons of modern LC pumps are made of sapphire to reduce wear and extend the working life of the pump. The cylinder is usually made of stainless steel, which incorporates two nonreturn valves in line with the inlet and outlet connections to the pump. The piston is driven by a... 

Leave valve protection caps in place and hand-tightened until cylinders are secured and in use (or connected for use). Some types of gas cylinders have valve outlet caps and plugs that form a gas-tight seal. Keep the device on the valve except when containers are secured and connected. 

The third basic valve outlet design, illustrated by Connection CGA 870, is shown in Fig. 9-4. This is a nonthreaded, pin-indexed yoke connection intended for use only on small medical gas cylinders. The specifications page in CGA V-1 for each connection of this type carries the connection number, rated pressure, and gas assignment. The necessary dimensions for manufacture are also given [1]. 

There are a number of different types of cylinder valves affixed to the cylinders that are deliverd to users. Regulators are attached directly to these cylinder valves by the user. Four commonly used types of cylinder valves are illustrated in Figs. 4-6 through 4-9. Many valve outlet and inlet connections have been standardized by the Compressed Gas Association for the different families of gases to prevent the interchange of regulator equipment between gases which are not compatible. These standardized connections have been adopted by the American National Standards Institute and the Canadian... 

The most common cylinder valve used for dichlorosilane is a stainless steel diaphragm valve with a Connection CGA 678 outlet. The cylinder valve body has a combination CG-4 type pressure relief device consisting of a fusible metal plug, melting about 165°F (74°C), which is protected from the cylinder contents by a frangible metal disk, i.e. a rupture disk, rated at 250 psig (1724 kPa). 

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